404 SUMMARY OF CURRENT RESEARCHES RELATING TO 



with sulphuric acid : Erythrophyll a — Bosa, Petunia, Dianihus, rasp- 

 berry, black currant, beet, radish ; ^ — Geranium, Gladiolus, Papaver 

 Phoeas, Fuchsia; y — Epilohium angustifolium ; 8 — Diervillea ; e — Caly- 

 canilius. Xanthophyll a — Crepis, Hieracium ; /3 — Linum campanula- 

 ceum ; y — Criiciferse ; S — Eanuculaceae ; e — Hypericum; t, — Lilium tigri- 

 num; -q — Zinnia; 6 — Tropseolum. Anthocyan a — Lunaria, Malva, Viola; 

 P — Lobelia, Campanula, Geranium pratense ; y — Gentiana acaulis ; 

 8 — (no example given); e — Centaurea Oyanus ; t, — Delphinium consolida. 



Change in Colour of Leaves containing Anthocyan.* — According 

 to Herr H, Molisch, the rapid loss of the colour of leaves which are 

 coloured purple by anthocyan, is due to the fact that anthocyan, or the 

 mixture of pigments known under this name, turns blue on the addition 

 of a trace of alkali, green with a larger quantity, then yellow, and 

 finally loses its colour entirely. On the death of the leaf or other 

 organ, this is brought about by the contents of the cells which con- 

 tained anthocyan mixing with the protoplasm of other cells from which 

 they were previously separated. 



Tannin-vacuoles.f — Herr J. E. F. af Klercker has carefully in- 

 vestigated the mode of formation of tannin in a large number of plants, 

 especially in the root. He finds that the tannin of the mature root 

 occurs partly dissolved in the entire cell-sap, partly in special re- 

 ceptacles or tannin-vacuoles, occasionally in the cell-wall, never in the 

 protoplasm. These vacuoles are formed in the protoplasm by the co- 

 alescence of small sap-cavities which contain tannin ; in the first place 

 vacuoles are formed in the protoplasm of the meristem-cells, some of 

 which contain tannin, others not. If their coalescence is prevented by 

 artificial means, abnormal vacuoles are formed. 



An excretion of mucilaginous tannin often takes place in the tannin- 

 vacuoles by plasmolysis. These vacuoles frequently, but not always, 

 contain, besides tannin, substances in appreciable quantities which 

 produce osmose. The tannin of the vacuoles, as well as that of many 

 other cells, shows no, or scarcely any, tendency towards osmose. Ail 

 the tannin-vacuoles which were examined took up methyl-blue. Albu- 

 minoids never occur in solution in these vacuoles. 



The tannin-vacuoles are, during the whole of their existence, inclosed 

 in a lamella of protoplasm, and are probably separated from it by a 

 precipitated membrane of iron-tannate. Both in the vacuoles and in 

 many other cases the tannin results from chemical decompositions in the 

 protoplasm of the meristem-cells, and makes its first appearance in the 

 form of solid granules in the protoplasm, which are afterwards dissolved 

 into a vacuole. The tannin of the vacuoles of the bark of the root, as 

 well as that of all root-caps, must be regai-ded as an excretion. In the 

 epiderm a resorption of these vacuoles frequently takes place in the 

 formation of the root-hairs. 



The tests for tannin employed by the author were the staining by 

 methyl-blue, and the precipitation by alkaline carbonates. He also 

 made use of a modification of Moll's reaction, consisting of the substitu- 

 tion of an alcoholic for an aqueous solution of copper acetate, whereby 

 the tannin was stained and the entire cell-contents fixed. 



A table is appended of the species in which tannin was observed, 



* Bot. Ztg., xlvii. (1889) pp. 17-23. 



t Bih. K. Svensk. Yet.-Akad. Handl., xiii. (1888) No. 8, G3 pp. (1 pi.). 



